The present invention relates to the art of fluid-tightly and rotatably supporting a shaft member in a water pump.
There is known a fluid-tight shaft mounting comprising a generally tubular housing through which the shaft member extends, a sealed bearing assembly positioned within the housing and exteriorly around the shaft member for the support of the shaft member relative to the housing, and a seal assembly interposed between a driven element, for example, an impeller of the water pump, and the bearing assembly and exteriorly around the shaft member, such as disclosed in, for example, U.S. Pat. No. 3,511,513, patented May 12, 1970.
According to the above mentioned U.S. patent, the seal assembly is employed in the form of a combination axial-mechanical face and radial seal element including a dynamic radial seal in sliding engagement with the peripheral surface of the shaft member and an axial-mechanical face seal including a ring-shaped seal seat rotatable together with the shaft member and a generally ring-shaped seal washer elastically biased so as to slidingly engage the seal seat. Between the bearing assembly and the combination face and radial seal element, there is formed an annular space which is communicated with the outside through a drain hole defined in the housing for the drainage of any leakage entering such annular space past the combination face and radial seal element.
The combination axial-mechanical face and radial seal used in the above mentioned U.S. patent is operable to prevent a fluid medium within, for example, the pump casing in which the impeller is disposed, from leaking into the bearing assembly. However, it has been found that the seal is not complete in that no fluid compressed enough to evolve heat can be prevented from leaking. In most pump applications, the fluid medium leaks past the combination face and radial seal and the bearing assembly in the form of a vapor.
As a matter of course, when a portion of the shaft member on one side of the combination face and radial seal opposite to the impeller is wetted with the water vapor leaking past the combination face and radial seal, rusting will be initiated on that portion of the shaft member, which will eventually constitute a cause of frictional wear of the seal elements used. Equally, when the vapor enters the bearing assembly, some component parts of the bearing assembly will rust to such an extent as to result in the counter-leakage of a lubricant from the bearing assembly into the pump casing past the combination face and radial seal, with the service life of the pump as a whole eventually reduced. This is because the vapor leaking past the seal assembly cannot be completely discharged to the outside of remains afloat around the shaft member.
In addition, the prior art fluid-tight shaft mounting such as disclosed in the above mentioned U.S. patent has another disadvantage in that, since the assembly of the shaft member with the bearing assembly and the combination axial-mechanical face and radial seal assembly are handled as members separate from each other, the mounting of the shaft member requires a complicated and time-consuming procedure.